Percy, who only became eligible for the 50-and-older tour in May, grabbed the 36th and final berth in the Charles Schwab Cup Championship in dramatic circumstances after he tied fifth in the penultimate playoffs event on Sunday.
He was seven under through 14 holes in the final round of the Simmons Bank Championship in Arkansas until three straight bogeys down the stretch moved him back outside the top 36.
It was so close that it took Miguel Angel Jimenez missing a 10-foot par putt on the last hole to fall out of a three-way tie for fifth. The extra money from a two-way tie moved Percy to 36th in the Schwab Cup standings to extend his season.
He joined fellow Australians Richard Green (ranked No.6), Greg Chalmers (No.28), Mark Hensby (No.29) Rod Pampling (No.33) and Stuart Appleby (No.34) in advancing.
But there was heartache for Australia's David Brandson who was bumped out of the top 36 as he finished tied 34th to be (No.38), missing out along with countrymen Steve Allan (No. 39) and Michael Wright (No.52).
Padraig Harrington closed with a five-under 67 and held on for a two-shot victory from Y.E. Yang, his third title this year on the PGA Tour Champions.
Harrington, who finished at 17-under 199 moved from No. 11 to No. 4, giving him a reasonable chance in Phoenix to win the Schwab Cup.
Top-ranked Ernie Els closed with a 65 and made up a seven-shot difference on New Zealand Steven Alker to keep the No.1 seed going into the finale.
